Melanoma and the nonmelanoma skin cancers arise from normal cells in the epithelial layer of the skin. Risk factors for skin cancers are complex and involve numerous inherited, environmental, and biological factors including selenoproteins that are involved in the response of the skin to UV-induced oxidative stress. Results from epidemiological studies of dietary, environmental, and supplemental sources of selenium suggest that in some cases selenium reduces, but in other cases increases, the risk for skin cancer in humans. Studies in model systems using compounds that can enter the "central selenium pool", thereby supporting the synthesis of selenoproteins, have also been mixed. It seems likely that there is a U-shaped curve for selenium intake and skin cancer risk, where the risk is highest at both deficient (<20 μg per day) and supranutritional levels.